Use correctly-sized buffer when zero-filling a WAL file.
Use correctly-sized buffer when zero-filling a WAL file.

I mixed up BLCKSZ and XLOG_BLCKSZ when I changed the way the buffer is
allocated a couple of weeks ago. With the default settings, they are both
8k, but they can be changed at compile-time.

pavanvd/postgres-xl,Postgres-XL/Postgres-XL,ashwinstar/gpdb,yazun/postgres-xl,50wu/gpdb,jmcatamney/gpdb,zeroae/postgres-xl,greenplum-db/gpdb,50wu/gpdb,adam8157/gpdb,ashwinstar/gpdb,jmcatamney/gpdb,ovr/postgres-xl,jmcatamney/gpdb,xinzweb/gpdb,xinzweb/gpdb,zeroae/postgres-xl,xinzweb/gpdb,xinzweb/gpdb,techdragon/Postgres-XL,lisakowen/gpdb,Postgres-XL/Postgres-XL,techdragon/Postgres-XL,yazun/postgres-xl,xinzweb/gpdb,jmcatamney/gpdb,oberstet/postgres-xl,lisakowen/gpdb,pavanvd/postgres-xl,jmcatamney/gpdb,adam8157/gpdb,oberstet/postgres-xl,50wu/gpdb,yazun/postgres-xl,greenplum-db/gpdb,greenplum-db/gpdb,adam8157/gpdb,ovr/postgres-xl,ovr/postgres-xl,50wu/gpdb,jmcatamney/gpdb,ovr/postgres-xl,50wu/gpdb,xinzweb/gpdb,greenplum-db/gpdb,adam8157/gpdb,lisakowen/gpdb,Postgres-XL/Postgres-XL,lisakowen/gpdb,techdragon/Postgres-XL,adam8157/gpdb,ashwinstar/gpdb,Postgres-XL/Postgres-XL,oberstet/postgres-xl,lisakowen/gpdb,greenplum-db/gpdb,techdragon/Postgres-XL,lisakowen/gpdb,greenplum-db/gpdb,pavanvd/postgres-xl,yazun/postgres-xl,ashwinstar/gpdb,xinzweb/gpdb,ashwinstar/gpdb,zeroae/postgres-xl,lisakowen/gpdb,adam8157/gpdb,50wu/gpdb,zeroae/postgres-xl,50wu/gpdb,ashwinstar/gpdb,yazun/postgres-xl,xinzweb/gpdb,ovr/postgres-xl,greenplum-db/gpdb,ashwinstar/gpdb,ashwinstar/gpdb,pavanvd/postgres-xl,zeroae/postgres-xl,techdragon/Postgres-XL,jmcatamney/gpdb,50wu/gpdb,oberstet/postgres-xl,jmcatamney/gpdb,adam8157/gpdb,pavanvd/postgres-xl,lisakowen/gpdb,greenplum-db/gpdb,oberstet/postgres-xl,Postgres-XL/Postgres-XL,adam8157/gpdb